44 Chapter Flashcards
(88 cards)
1
Q
Osmoregulation
A
The general term for the processes by which animals control solute concentration and balance water gain and loss.
2
Q
Excretion
A
The process that rids the body of nitrogenous metabolites and other metabolic waste products
3
Q
Ammonia
A
A toxic metabolite produced by the dismantling of nitrogenous molecules, chiefly proteins and nucleic acids
4
Q
Ultimately, the driving force for the movement of both water and solutes—in animals as in all other organisms—is a concentration gradient of one or more solutes across the plasma membrane.
A
True
5
Q
The unit of measurement for solute concentration is ____________
A
Osmolarity
6
Q
Osmolarity
A
The number of moles of solute per liter of solution
7
Q
The osmolarity of human blood is…
A
About 300 milliosmoles per liter (mOsm/L), whereas that of seawater is about 1000 mOsm/L
8
Q
Isoosmotic
A
Two solutions with the same osmolarity
9
Q
Hyperosmotic
A
The solution, of two, with the higher concentration of solutes and lower free H2O concentration
10
Q
Hypoosmotic
A
The solution, of two, with lower solute concentration and higher free H2O concentration.
The more dilute solution
11
Q
Water flows by osmosis from a hypoosmotic solution to a hyperosmotic one.
A
True
12
Q
An animal can maintain water balance in two ways:
A
To be an osmoconformer or to be an osmoregulator
13
Q
Osmoconformer
A
An animal that is isoosmotic with its environment.
14
Q
Osmoregulator
A
An animal that controls its internal osmolarity independent of the external environment.
15
Q
All osmoconformers are __________
A
Marine animals
16
Q
Stenohaline
A
Refers to animals that cannot tolerate substantial changes in external osmolarity
17
Q
Euryhaline
A
Refers to animals that can survive large fluctuations in external osmolarity.
18
Q
The body fluids of freshwater animals must be ____________ because animal cells cannot tolerate salt concentrations as low as that of lake or river water.
A
Hyperosmotic
19
Q
Dessication
A
Extreme dehydration
20
Q
Anhydrobiosis
A
A dormant state involving loss of almost all body water
21
Q
Transport epithelia
A
One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions.
22
Q
Animals excrete nitrogenous wastes as…
A
Ammonia, urea, or uric acid
23
Q
Ammonia excretion is most common in ________________
A
Aquatic species
24
Q
Urea
A
A soluble nitrogenous waste produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide.
25
Guano
Bird droppings, a mixture of white uric acid and brown feces
26
Uric acid
A product of protein and purine metabolism and the major nitrogenous waste product of insects, land snails, and many reptiles. It is relatively nontoxic and largely insoluble in water.
27
Four key steps of an excretory system function
Filtration
Reabsorption
Secretion
Excretion
28
Filtration
In excretory systems, the extraction of water and small solutes, including metabolic wastes, from the body fluid
29
Filtrate
Cell-free fluid extracted from the body fluid by the excretory system
30
Reabsorption
In excretory systems, the recovery of solutes and water from filtrate. The transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluids.
31
Secretion
In an excretory system, the active transport of wastes and certain other solutes from the body fluid into the filtrate
32
Protonephridia
The excretory system of flatworms. Form a network of dead-end tubules.
33
Coelom
Body cavity
34
Metanephridia
An excretory organ found in many invertebrates that collects fluid directly from the coelom.
35
Malphigian tubules
A unique excretory organ of insects that empties into the digestive tract, removes nitrogenous wastes from the hemolymph, and functions in osmoregulation.
36
Kidneys
In vertebrates, a pair of excretory organs where blood filtrate is formed and processed into urine. They also transport and store urine.
37
Ureter
A duct leading from the kidney to the urinary bladder.
38
Urinary bladder
The pouch where urine is stored prior to elimination
39
Urethra
A tube that releases urine from the mammalian body near the vagina in females and through the penis in males; also serves in males as the exit tube for the reproductive system
40
____________ near the junction of the urethra and bladder regulate urination.
Sphincter muscles
41
Renal cortex
The outer portion of the vertebrate kidney.
42
Renal medulla
The inner portion of the vertebrate kidney, beneath the renal cortex
43
Renal pelvis
The funnel-shaped chamber that receives processed filtrate from the vertebrate kidney’s collecting ducts and is drained by the ureter
44
Nephrons
The tubular excretory unit of the vertebrate kidney. Includes the functional units of the vertebrate kidney.
45
Cortical nephrons
In mammals and birds, a nephron with a loop of Henle located almost entirely in the renal cortex. Makes up roughly 85% of nephrons in a human kidney.
46
Juxtamedullary nephrons
In mammals and birds, a nephron with a loop of Henle that extends far into the renal medulla
47
Glomerulus
A ball of capillaries surrounded by Bowman’s capsule in the nephron and serving as the site of filtration in the vertebrate kidney.
48
Bowman’s capsule
A cup-shaped receptacle in the vertebrate kidney that is the initial, expanded segment of the nephron, where filtrate enters from the blood.
49
Processing occurs as the filtrate passes through three major regions of the nephron:
The proximal tubule, the loop of Henle, and the distal tubule
50
Proximal tubule
In the vertebrate kidney, the portion of a nephron immediately downstream from Bowman’s capsule that conveys and helps refine filtrate
51
Loop of Henle
The hairpin turn, with a descending and ascending limb, between the proximal and distal tubes of the vertebrate kidney; functions in water and salt reabsorption
52
Distal tubule
In the vertebrate kidney, the portion of a nephron that helps refine filtrate and empties it into a collecting duct
53
Collecting duct
The location in the kidney where processed filtrate, called urine, is collected from the renal tubules.
54
Afferent arteriole
An offshoot of the renal artery that branches and forms the capillaries of the glomerulus. Supplies blood to each nephron.
55
Efferent arteriole
The convergence of capillaries as they leave the glomerulus.
56
Peritubular capillaries
One of the tiny blood vessels that form a network surrounding the proximal and distal tubules in the kidney. Play a key role in reabsorption.
57
Vasa recta
The capillary system in the kidney that serves the loop of Henle.
58
The porous capillaries and specialized cells of Bowman’s capsule are permeable to water and small solutes, but not blood cells or large molecules, such as plasma proteins. Thus, the filtrate produced in the capsule contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules. Because such molecules pass freely between glomerular capillaries and Bowman’s capsule, the concentration of these substances in the initial filtrate are the same as those in blood plasma.
True
59
Processing of filtrate in the proximal tubule helps maintain a relatively constant pH in body fluids. How?
Cells of the transport epithelium secret H+ into the lumen of the proximal tubule and synthesize and secrete ammonia, which acts as buffer to trap H+ in the form of ammonium ions (NH4+). Proximal tubules also reabsorb about 90% of the buffer bicarbonate (HCO3-) from the filtrate, contributing further to pH balance in body fluids.
60
Reabsorption of water continues as the filtrate moves into the descending limb of the loop of Henle. In contrast, there are almost no channels for salt and other small solutes, resulting in very low permeability for these substances.
True
61
The filtrate loses water and increases in solute concentration all along its journey down the descending limb.
True
62
Unlike the descending limb, the ascending limb has a transport epithelium that lacks water channels.
True
63
The ascending limb has two specialized regions:
A thin segment; near the loop tip
A thick segment; adjacent to the distal tubule
64
Changes in osmolarity as filtrate moves through the loop of Henle
In the descending limb, reabsorption of water occurs. In the thin segment of the ascending limb, NaCl, which became concentrated in the descending limb, diffuses out of the permeable membrane tubule into the interstitial fluid of the inner medulla. In the thick segment of the ascending limb, the movement of the NaCl out of the filtrate continues; however, the epithelium actively transports NaCl into the interstitial fluid.
65
The distal tubule plays a key role in…
Regulating the K+ and NaCl concentration of body fluids.
66
Final processing of the filtrate by the transport epithelium of the collecting duct forms the urine.
True
67
The state of the collective duct epithelium is controlled by hormones that together maintain homeostasis for osmolarity, blood pressure, and blood volume.
True
68
The nephrons—particularly the loops of Henle—can be thought of as energy-consuming machines that produce an osmolarity gradient suitable for extracting water from the filtrate in the collecting duct.
True
69
Counter-current multiplier systems
Are countercurrent systems, which expend energy to create concentration gradients; such as the thick segment in the ascending limb of the loop of Henle
70
Two solutes contribute to the osmolarity of the interstitial fluid:
NaCl and urea
71
Divalent ions
Those with a charge of 2+ or 2-
72
Monovalent ions
Charge of 1+ or 1-
73
Antidiuretic hormone (ADH), AKA vasopressin
ADH is a hormone produced by the hypothalamus and released by the pituitary gland. It plays a crucial role in regulating the body’s water balance.
74
When is ADH released into the bloodstream and what does it do?
ADH is released into the bloodstream when the body senses that it needs to conserve water such as during dehydration, when blood osmolarity rises, or in the case of low blood volume. ADH then acts on the kidneys, specifically the collecting ducts, to increase their permeability to water. This allows more water to be reabsorbed from the filtrate back into the bloodstream, reducing urine volume and concentrating the urine.
75
As the osmolarity of blood falls, a negative-feedback mechanism reduces the activity of osmoreceptor cells in the hypothalamus, and ADH secretion is reduced.
True
76
Diuresis
A high level of urine production
77
Renin-angiotensin-aldosterone system (RAAS)
A hormone cascade pathway that helps regulate blood pressure and blood volume.
78
Juxtaglomerular apparatus (JGA)
A specialized tissue in nephrons that releases the enzyme renin in response to a drop in blood pressure or volume. Consists of cells of and around the afferent arteriole.
79
Renin
An enzyme that initiates a sequence of steps that cleave a plasma protein called angiotensin, ultimately yielding a peptide called angiotensin II.
80
Angiotensin II
A peptide hormone that stimulates constriction of precapillary arterioles and increases reabsorption of NaCl and water by the proximal tubules of the kidney, increasing blood pressure and volume.
81
Aldosterone
A steroid hormone that acts on the tubules of the kidney to regulate the transport of sodium ions (Na+) and potassium ions (K+). Increases blood volume and pressure.
82
Because angiotensin II acts in several ways that increase blood pressure, drugs that block angiotensin II production are widely used to treat hypertension.
True
83
The renin-angiotensin-aldosterone system operates as a feedback circuit. A drop in blood pressure and blood volume triggers renin release. The resulting production of angiotensin II and release of aldosterone cause a rise in blood pressure and volume, reducing the release of renin from the JGA.
True
84
The release of ADH is a response to…
An increase in blood osmolarity.
85
What does the RAAS respond to that ADH does not?
A drop in blood volume without increasing osmolarity.
86
Atrial natriuretic peptide (ANP)
A peptide hormone secreted by cells of the atria of the heart in response to high blood pressure. ANP’s effects on the kidney alter ion and water movement and reduce blood pressure.
87
The walls of the atria of the heart release ANP in response to…
An increase in blood volume and pressure
88
How does ANP affect the JGA, collecting ducts, and adrenal glands?
ANP inhibits the release of renin from the JGA, inhibits NaCl reabsorption by the collecting ducts, and reduces aldosterone release from the adrenal glands. These actions lower blood volume and pressure.
